This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Sage consists of the leaves of Salvia officinalis, or common garden sage, an undershrub of two feet or more in height, originally from the South of Europe, but cultivated everywhere in gardens. They have a strong fragrant odour, and a warm, bitterish, aromatic, and somewhat astringent taste. They contain tannic acid, and probably a bitter principle; but their virtues depend mainly on a volatile oil, which exists in them in large proportion.
The virtues of sage are those of a gentle tonic and astringent, and an efficient aromatic. In addition to its excitant influence upon the digestive organs and the circulation, it has been supposed also to stimulate the nervous and genital systems, and, when suitably aided, no doubt promotes perspiration. By the ancients it was very highly esteemed, and retained its credit as a remedy among the earlier modern Europeans, as evinced by the dictum of the school of Salerno, "Cur moriatur homo cui Salvia crescit in horlo." It was used as a stimulant tonic in weakness of digestion and general debility, as an astringent in checking profuse sweats and excessive lacteal secretion, as a febrifuge in paroxysmal fevers, as a diaphoretic in catarrh, and as an antispasmodic in various nervous affections. From these over-estimates of its virtues, it has fallen into probably unmerited disrepute, and has been abandoned by the British authorities, though retained in our own Pharmacopoeia. It may be used with advantage as an antiemetic, carminative, and gentle stimulant to the stomach and bowels, especially when there is enfeebled digestion, with a tendency to diarrhoea But the chief use now made of it medicinally is as a gargle in common sore-throat, and relaxation of the uvula, for which purpose it is employed in the form of infusion, and often associated with honey, and alum or vinegar. It is much used as a condiment in cookery, especially in the filling of roasted poultry, and in sausages. As a gargle, and when all its effects on the system are demanded, the infusion should be prepared by macerating an ounce of the leaves in a pint of boiling water, and the maceration continued till it cools. Two fluidounces may be given for a dose. When wanted to relieve nausea, or as an agreeable drink in febrile affections, the proportion of sage should be lessened, and the maceration shortened, so that the whole of the bitterness may not be extracted. The officinal Infusion (Infusum Salvia, U. S.) is made with half an ounce to the pint.